Since optical discs such as a CD (Compact Disc) and a CD-ROM (Compact Disc Read Only Memory) are easy to handle and are produced at relatively low cost, they have been widely used as recording mediums for storing data. In recent years, a CD-R (Compact Disc Recordable) disc, on which data can be recorded once, and a CD-RW (Compact Disc ReWritable) disc, on which data can be rewritten, have come out. Thus, data can be easily recorded on such recordable optical discs. As a result, optical discs that accord with the CD standard such as a CD-DA (Compact Disc Digital Audio) disc, a CD-ROM disc, a CD-R disc, and a CD-RW disc have become the mainstream of data recording mediums. In addition, in recent years, audio data is compressed according to the MP3 (MPEG1 Audio Layer-3) and the ATRAC (Adaptive TRansform Acoustic Coding) 3 and recorded on the CD-R disc, the CD-RW disc, and so forth.
However, as a CD-R disc and a CD-RW disc have come out, data recoded on a CD disc can be easily copied to these discs. As a result, a problem about copyright protection has arisen. Thus, when content data is recorded to a CD disc, it is necessary to take measures to protect content data.
As a conventional copy protection technology for protecting a copy of data from a CD-ROM disc to a CD-R disc or a CD-RW disc, a method for physically deforming a disc with for example wobble pits has been proposed. In the physically deforming method, however, if an original disc is a CD-R disc or a CD-RW disc, the copy protection cannot be performed.
In addition, to protect a copying operation, a method for encrypting content data has been proposed. However, even if content data has been encrypted, a disc on which the same data as an original disc is recorded can be produced.
To protect content data recorded on a CD disc that accords with the CD standard, there is a method for determining whether the disc is an original CD or a CD whose data has been copied from an original CD (this CD is referred to as copied CD). When the disc is an original CD, a copying operation thereof can be permitted. When the disc is a disc whose data has been copied from an original disc (this disc is referred to as copied disc), a further copying operation thereof can be prohibited.
To determine whether the disc is an original disc or a copied disc, a method for placing a defect on a disc in a master disc production stage, detecting the defect from the disc during a reproduction, and determining that the disc is an original disc based on the detected defect has been proposed. In this method, however, an original disc may contain such a defect. In addition, depending on the type of a defect, it may be copied as it is. Thus, content data of an original disc cannot be prevented from being copied to a CD-R disc.
Therefore, an object of the present invention is to provide a data recording medium, a data recording method, and a data recording apparatus that contribute to copy protection without need to physically deform a medium and intentionally place a defect thereon.